The Mystery of the Fiery Eye (Alfred Hitchcock and the Three Investigators #7)

Three junior detectives solve a mystery involving a collection of antique busts, a legacy, a strange letter, and a red ruby.

Long Synopsis:

The three investigators must solve an old man's riddle to uncover a great fortune for their friend, Gus. But they're racing against a sinister bunch of treasure hunters who are also hot on the trail. Who will arrive first at the "Mysterious Fiery Eye"?